In motor vehicles, which are driven by internal combustion engines, the engine is cooled with a liquid coolant so that the engine does not exceed a critical temperature. The heated coolant can be conducted through a latent heat accumulator and there transfer its heat so that the accumulator is charged. The latent heat accumulator can store the received heat quantity extremely long (approximately 48 hours) and the stored heat quantity can be used for different purposes. For example, the stored heat can be used to prewarm the engine in advance of starting or to prewarm the passenger compartment and/or to preheat a catalytic converter, et cetera.
In modern motor vehicles, and especially in motor vehicles, which are equipped with modern direct-injecting turbo diesel engines, the efficiency of the engine becomes ever greater, that is, the heat outputted by the engine becomes less. This efficiency is desirable but can lead to a situation wherein the emitted heat of the engine is no longer sufficient to adequately heat the liquid coolant and therefore the latent heat accumulator, so that the accumulator can no longer satisfactorily fulfill its function. A further difficulty is that the heated coolant must be conducted to the latent heat accumulator with the least possible heat loss. For this purpose, the latent heat accumulator either must be positioned as close as possible to the engine, which can introduce problems because of the tight engine compartment of modern motor vehicles or, a longer transport path must be accepted which requires a complex and therefore expensive thermal insulation of this path.